Knife guards for sewing machines



Apxrifi 5, 1950 B. P. PINKVOSS ETAL 2,931,330

KNIFE GUARDS FOR sswmc MACHINES Filed April 15, 1958 2 Sheets-Sheet 1 Fig! 38 INVENTORS 30 William Mayeran 43 4O Benhold P Pinkvoss,Deceased WITNESS 4? 28 Agnes Pinkvoss, Execufrix WZQLM Fig.4 BY Wg Aprfl 5, 1960 B. P. PmKvoss ETA!- 2,931,330

KNIFE GUARDS FQR SEWING MACHINES 2 Sheets-Sheet 2 Filed April 15, 1958 INVENTORS a m Y m" E U N c R v m S T n 0% Q/ r e w W/mV M M M ws a Ihe ldln W WITNESS m KNIFE GUARDS FOR SEWING MACHINES Berthold P. Pinkvoss, deceased, late of Stratford, Conn., by Agnes Piukvoss, executrix, Stratford, and William Mayeran, Fair-field, Conn., assignors to The Singer Manufacturing Company, Elizabeth, N.J., a corporation of New Jersey Application April 15, 1958, Serial No. 728,653

4 Claims. (Cl. 112-261) This invention relates to sewing machines having work trimming knives, and more particularly, to guard means for preventing injury to the sewing machine operator by accidental contact with the knife blade.

It is an object of this invention to provide a knife guard for shielding the sewing machine operator from accidental contact with a work trimming knife blade when the knife blade has been shifted to an inoperative position to facilitate introduction and removal of the work.

It is another object of this invention to provide a knife guard of the above character which is biased into a retracted position so as not to interfere with work manipulation when the knife occupies an operative position.

Still another object of this invention is to provide a means automatically for shifting the knife guard out of retracted position and into effective knife guarding position whenever the knife blade is thrown out of operative position.

In the accompanying drawings which illustrate a preferred form of this invention:

Fig. 1 represents a side elevational view of a work supporting post of a sewing machine having a work trimming knife and a knife guard of this invention applied thereto,

Fig. 2 represents an enlarged end elevational view of the sewing machine work supporting post of Fig. 1 with the knife illustrated in an operative position,

Fig. 3 represents an end elevational view of a portion of the sewing machine work supporting post illustrated in Fig. 2 but the knife blade thrown out into inoperative position and the knife guard in effective position to guard the knife cutting edge,

Fig. 4 represents a top plan view of the sewing machine work supporting post of Fig. l, and

Fig. 5 represents a top plan view of the upper portion of the sewing machine work supporting post with the knife and the knife guard being illustrated in both operative and inoperative positions.

in the drawings, this invention is illustrated as applied to a fabric trimming mechanism of the type referred to in the art as a Barber trimmer used on a sewing machine having an upstanding work supporting post 11. The post 11 rises from a machine bed 12 and is fitted with a work feeding wheel 13 driven in conventional fashion as well as with a looper (not shown) adapted to cooperate with an endwise reciprocatory needle 14 in the formation of stitches. The needle as well as a driven roller presser 15 may be carried by a conventional bracket arm (not shown) which rises from the bed 12 and overhangs the post 11.

The work trimming mechanism has a knife member 20 secured by screws 21 to a knife carrier 22 to extend substantially horizontally over the post 11. At the free extremity, the knife member is formed with a depending lip 23 which is sharpened and provides the knife blade for severing the work. The knife carrier 22 is nitcd States Patent 0 2,931,330 Patented Apr. 5, 1960 secured to a tubular knife drive shaft 24 journaled on a vertical axis in bushings 25 on the post 11. Secured on the lower extremity of the knife drive shaft 24 by a clamp screw 26 is a rock arm 27 carrying at its free extremity a spring loaded plunger 28 which seats in a socket 29 formed in one arm 30 of a bell crank 31 fulcrumed on the machine bed coaxially with the knife drive shaft 24. The other arm 32 of the bell crank 31 carries a bifurcated follower 33 which embraces a block 34 journaled on an eccentrically disposed pin 35 formed on the end of a rotary knife-actuating shaft 36 journaled on the machine bed.

A push rod 37 is slidably within the hollow knife drive shaft 24 and is operatively connected at its lower extremity with a lever 38 fulcrumed at 39 on the rock arm 27. The lever 38 is aperture'd to receive the plunger 28 and a nut 49 threaded on the plunger maintains the plunger in operative connection with the lever. Thus, by depression of the push rod 37, the machine operator may withdraw the plunger 28 from the socket 29 in the driving bell crank 31 and disconnect the trimmer drive. A torsion spring 41 about the knife drive shaft is anchored at one extremity against the work supporting post and at the other extremity in a collar 42 fast on the knife drive shaft to bias the shaft in a clockwise direction as viewed in Figs. 4 and 5 so that when the push rod 37 is depressed, the knife member 20 will swing to an inoperative throw-out position, as is illustrated in Fig. 3 and in dashed lines in Fig. 5. The throw-out position is determined by a stop lug 43 formed on the rock arm 27 which strikes a cover 44 for the rotary knife actuating shaft 36.

An operator influenced lever 45 is held fast on the knife drive shaft by a clamp screw 46 so that the knife member 20 may be turned by the operator in a counterclockwise direction, as viewed in Figs. 4 and 5, into an operative position. The bell crank arm 30 is inclined, as at 47, leading to the socket 29 so that the plunger 28 will ride gradually upward and into the socket 29 without binding. The action of theplunger seating in the socket of the bell crank will lock the knife member in an operative position in which the sharpened lip 23 is disposed over the post and opposite the path of the needle 14, as is illustrated in Figs. 1, 2, 4 and in full .lines in Fig. 5.

When the knife is in operative position, the cutting edge on the lip 23 is well shielded by the post beneath the knife and the knife member itself which covers the cutting edge. When the knife is in throw-out position, however, as viewed in Fig. 3, the cutting edge is exposed and if not shielded, a serious injury may be inflicted upon an operator particularly during the natural hand move ments necessary to introduce an article to the stitching point.

A guard, if permanently fixed so as to shield the cutting edge in throw-out position, would however constitute a serious impediment to manipulation of work fabrics on the post during stitching and would thereby minimize the advantages of convenient work handling which is perhaps one of the basic reasons for the existence of post machines.

The knife guard of this invention provides an effective shield for the knife cutting edge when the knife occupies the throw-out position and, as shown in Figs. 2 and 4, the knife guard is retracted against the post when the knife is in operative position so as not to interfere with work handling. The knife guarding mechanism of this invention comprises a guard member preferably in the form of a rod 50 which is held in a substantially vertical plane by means of a block 51 formed with a bore 52 for the rod 50 and a set screw 53 to hold the rod in place in eastern 3 the block. The block 51 is journaled on a stud 54 which is secured on a substantially horizontal axis in a bracket 55 carried by screws 56 on' the side of the post 11. A spring 57 secured on the bracket 55 is formed with an arm 58 engaging the rod 50 to bias the rod into retracted position against the post, as is illustrated in Figs. 1, 2, 4 and in full lines in Fig. 5. i i

A knife guarding finger 59 is formed on the upper extremity of the rod 50 and extends substantially horizontally.

A cam follower 60 formed onthe block 51 engages a cam lug 61 formed on the hub of the operator infiuenced lever 45 so that as the shaft 24 is turned into inoperative position of the knife, the cam lug 61 will cooperate with thecam follower 60 to shift the knife guarding finger outwardly to a position underlying the ic'uttingedg'e on-ithe lip 23. Such a shift of the knife guard will occur'automatically upon depression of the push may by the operator since the torsion spring41 is preferably: considerably stronger than the knife guard returnspring 57. Conversely, when the operator turns the lever 45 to bring the knife into operative position, the spring 57 will retract the knife guardagainst the post so 7 as not-to interfere with work handling.

ment into and out of a position shielding said knife in v 'the inoperative throw-out position of said knife, and a means associated with said work trimming mechanism operative upon movement of said knifeinto said inoperative throw out position to shift said knife guard into said elfective knife shielding position.

2. In a sewing machine having a frame and a stitching point t on said frame, a work trimming mechanism including a knife, meansfor imparting vibratory work cutting movements to said knife, and means for shiftably supporting said knife on said frame for bodily movement into'either an operative work severing position adjacent said stitching point or an inoperative throw-out position,

a knife guard, means for shiftably supporting said knife guard on said frame for movement into either an effective position shielding said knife in the inoperative throwout position of said knife or a retracted position, and

means operatively connecting said work trimming mechanism with said knife guard for shifting said knife guard into effective knife shielding position upon movement of said knife into inoperative position and for shifting said knife guard into retracted position upon movement of said knife into operative work severing position.

3. In a sewing machine having a frame and a stitching point'on said frame, a work trimming mechanism including a knife pivotally supported on said frame and having an operative position adjacentsaid stitching point, means for imparting work severing oscillation to said knife about said pivotal support, and means for turning said knife beyond the'range of said work severing oscillation into an inoperative throw-out position, a knife guard, means'pivotally supporting said knife on said frame for movement into either a retracted position or an effective position shielding said knife in the inoperative throw-outposition of said knife, spring means biasing said knife guard into retracted position, and cam means carried by said work trimming lmechanisrn 'and effective upon movement of said knife into inoperative throw-out position to engage and shift said knife guard into effective knife shielding position.

' 4. In a sewing machine having a vertical work supporting post, and a work trimming mechanism including a knife drive shaft journaled vertically along said post, an oscillatory work trimming knife carried on said knife drive shaft and disposed above the level of said post, a vertical knife blade formed on said knife and means forturning said shaft to carry saidknifeblade into an operative position over said post or to an inoperative position at one side of said post, means for guarding said knife blade in the inoperative position thereof, comprising a knife guard member, means for pivoting said knife guard member on a horizontal ax'is'at one side of said post,.

from said post and into a position adjacent said knife blade.

References Cited in the file of this patent UNITED STATES PATENTS 

